Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing liquid or solid sample
Reexamination Certificate
1999-05-17
2001-12-18
Snay, Jeffrey (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing liquid or solid sample
C422S082110, C436S525000
Reexamination Certificate
active
06331276
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to sensors such as an immuno sensor, gas sensor or ion sensor using surface plasmon resonance phenomenon, and to a device using these sensors.
The surface plasmon is a propagating wave of collectively oscillating free electrons at an interface between a thin metallic film and a dielectric material. As the propagation of the wave is sensitively influenced by the dielectric constant at the interface, it forms a basis for a detection principle in immuno sensors and gas sensors. A typical structure of such a sensor is shown in
FIG. 2A. A
thin metallic film
21
made of free electron metal such as gold or silver with thickness of approximately 50 nm is formed on the surface of a prism with a high refractive index, and which in addition to the thin metallic film
21
has a molecule recognition layer
29
. To generate the surface plasmon at the surface of the thin metallic film
21
, the film
21
must be irradiated from the prism side by p polarized collimated monochromatic light
22
from a light source
23
at a particular angle called resonance angle. Generation of the surface plasmon is monitored by detecting specularly reflected light
25
with a detector
26
. In other words, as shown in
FIG. 2B
, when the incident angle matches the resonance angle
27
at which the surface plasmon is excited, the intensity
28
of the reflected light becomes extremely small because a large portion of the energy in the incident light becomes transferred to the surface plasmon. The resonance angle depends on the dielectric constant at the surface; when change in the dielectric constant is induced at the surface of the thin metallic film
21
, the intensity
31
of the reflected light now decreases at a new resonance angle
30
. Because the resonance angle depends only on the dielectric constant within the region of several hundreds of nm from the surface, adsorption of a small amount of sample is enough to shift the resonance angle. Now if a device is constructed with a molecule recognition layer
29
capable of recognizing and binding a specific molecule, and if a sample fluid is allowed to flow over the surface, the dielectric constant will vary if a specific molecule in the sample fluid is bound. Hence, by observing the light reflected around the resonance angle, it can immediately be known if the specific molecule has been captured by the molecule recognition layer
29
.
In order to make use of the surface plasmon phenomenon associated with a thin metallic film, apart from the above collimated monochromatic light, a method (1) is known where the film is irradiated by divergent monochromatic light and the reflected light is measured by a light sensor array, and a method (2) where the film is irradiated by collimated white light, and the reflected light is measured by a spectrometer. In both methods it is the dependence of the resonance angle for light of a specific wavelength on the dielectric constant of the interface which is used.
SUMMARY OF THE INVENTION
In the measuring apparatus using surface plasmon resonance phenomenon of the prior art, the relative position of the light source, thin metallic film, and light detector must be accurately held as well as smoothly driven mechanically when required. To improve measurement accuracy, it is desirable to increase the distance between the thin metallic film and the light detector, but this precludes compact construction of the apparatus. Further, as the surface plasmon resonance method is sensitive to temperature, temperature control or correction for a drift in temperature is required, which also prevents the apparatus from being made compact. Another optical phenomenon associated with a free electron metal is localized surface plasmon. When particles made of a free electron metal, such as gold particles, are irradiated with white light, free electrons in the particles are induced to collectively oscillate within the confine of the particles at a certain frequency. This type of collective oscillation does not propagate, thus known as localized surface plasmon.
The plasmon resonance wavelength is known to depend on the dielectric constant in the near-field optical region within several fractions of a particle diameter away from the particle surface, and a method of detecting biological molecules using this technique is also known (Science, 277, 1078, 1997).
In principle, it is possible to enhance the near field intensity by changing the shape of the gold particles to an ellipsoid (Surface Science, 156, 678, 1985). It is also known that the strong near field intensity is generated around the end of a sharp metal tip when positioned in the vicinity of a metal substrate and irradiated (J. Vac. Sci. Technol., 9, 510, 1991).
Based on the idea that sharp tips and elongated particles have the same effect, the inventor found that when cap-shaped gold particles were formed near a metal substrate, much stronger coloration than that associated with the gold particles of the prior art was observed. Enhanced coloration implies that the near field intensity around the surface adsorbed cap-shaped gold particles is rather enhanced. Thus, a device based on the principle of simply measuring change in the absorption spectrum induced by adsorption of molecules on the particle surface within the near field can be simpler and more compact than a conventional surface plasmon sensor. This invention aims to provide a sensor and a measuring apparatus which is compact and easy to handle, and which is based on the coloration change of the new particles.
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patent: 4481091 (1984-11-01), Brus et al.
patent: 5023139 (1991-06-01), Birnboim et al.
patent: 5151956 (1992-09-01), Bloemer
patent: 5567628 (1996-10-01), Tarcha et al.
patent: 6180415 (2001-01-01), Scfhultz et al.
patent: 798561 (1997-10-01), None
patent: 2256477 (1992-12-01), None
patent: WO9809153 (1998-03-01), None
Journal Vacuum Science Technology, vol. B9, No. 2, Mar./Apr., 1991, “Near-field Optics: Microscopy with Nanometer-size fields” W. Denk et al, pp. 510-513.
Science, vol. 277, Aug. 22, 1997, “Selective Colorimetric Detection of Polynycleotides Based on the Distance-Dependent Optical Properties of Gold Nanoparticles”, R. Elghanian et al, pp. 1078-1081.
Journal of Vacuum Science and Technology, B9, No. 2, Mar./Apr. 1991, “Near-field optics: Microscopy with nanometer-size fields”, W. Denk et al, pp. 510-513.
Surface Science, 156, 1985, “Optical Absorption of Small Metallic Particles”, U. Kreibig, pp. 678-700.
Sakamoto Takeshi
Takei Hiroyuki
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
Snay Jeffrey
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